Global Warming Increases Monthly Heat Records Worldwide

According to a new study, there are now five times as many record-breaking hot months worldwide than could be expected without long-term global warming.

Jan 15, 2013

Monthly temperature extremes have become much more frequent, as measurements from around the world indicate. On average, there are now five times as many record-breaking hot months worldwide than could be expected without long-term global warming, shows a study now published in Climatic Change. In parts of Europe, Africa and southern Asia the number of monthly records has increased even by a factor of ten.

"The last decade brought unprecedented heat waves; for instance in the US in 2012, in Russia in 2010, in Australia in 2009, and in Europe in 2003," said lead-author, Dim Coumous. "Heat extremes are causing many deaths, major forest fires, and harvest losses -- societies and ecosystems are not adapted to ever new record-breaking temperatures."

The researchers developed a robust statistical model that explains the surge in the number of records to be a consequence of the long-term global warming trend. That surge has been particularly steep over the last 40 years, due to a steep global-warming trend over this period. If global warming continues, the study projects that the number of new monthly records will be 12 times as high in 30 years as it would be without climate change.

"Statistics alone cannot tell us what the cause of any single heat wave is, but they show a large and systematic increase in the number of heat records due to global warming," says Stefan Rahmstorf, a co-author of the study and co-chair of PIK's research domain Earth System Analysis. "Today, this increase is already so large that by far most monthly heat records are due to climate change. The science is clear that only a small fraction would have occurred naturally."